In a rolling bearing used, for example, in a speed retarder of a rolling mill or a press machine, since abrupt fluctuation of load occurs repetitively in the radial direction, rolling elements formed in a cylindrical or conical shape are used as rolling elements assembled between an outer bearing ring and an inner bearing ring. A cage for retaining rolling elements of such rolling bearings (hereinafter referred to as a “roller bearing”) includes various types and those referred to as a pin-type cage are constituted such that one ends of pins inserted through the central hole of a roller (rolling element) is fitted into pin-receiving holes formed in one annular side plate of a pair of annular side plates opposed to each other while putting the roller therebetween, and the annular side plate and the pins are welded so as to cover the entire end faces of the pins that are fitting into the pin-receiving holes as disclosed, for example, in JP60-182525U or JP11-325063A.
However, in the pin-type cage described above, as shown in FIG. 49, since the hole diameter of the pin-receiving hole 4 is larger than the outer diameter of the end of the pin 2, a gap g is formed between the pin-receiving hole 4 formed in the annular side plate 3 and the pin. Therefore, when a load in the radial direction is applied on the pin 2, stress concentration occurs to a weld portion 6 for the pin 2 and the annular side plate 3 to possibly cause fracture such as cracking due to stress concentration caused to the weld portion 6.
Further, in the existent pin-type cage, since the annular side plate 3 and the pin 2 are welded so as to cover the entire end face of the pin 2 fitting into the pin-receiving hole 4 in order to prevent cracking or the like in the weld portion due to stress concentration, a residual tensile stress is generated to the weld portion 6 for the pin 2 and the annular side plate 3 to result in a problem of lowering the strength.
Further, in the pin-type cage described in JP11-325063A, when a rolling element moves largely toward the annular side plate and is in contact with the pin, it may be sometimes in contact with a portion with no surface hardening layer or a portion where the depth of the surface hardening layer is shallow. Further, at the pin surface where the surface hardening layer is not formed, the mechanical strength to the bending stress is also low in addition to the wear resistance, compared with a portion where the surface hardening layer is formed.